Field of the Invention
The present invention relates to a technique of correcting the in-focus position obtained by a phase difference detection method based on the in-focus position detected by a contrast detection method.
Description of the Related Art
Conventionally, there is known a technique of performing focus detection by the phase difference detection method of detecting the focus state (defocus amount) of an imaging optical system from the phase difference between a pair of images formed by light passing through the imaging optical system in an interchangeable lens in a lens-interchangeable image capturing apparatus such as a single-lens reflex camera. Such a phase difference detection method has a problem that an in-focus position may not be accurately detected due to the influences of a light source, the color or the type of an object, or the like at the time of imaging.
In order to solve such a problem, Japanese Patent Laid-Open No. 2003-295047 discloses a camera having a focus calibration function for correcting the in-focus position obtained by the phase difference detection method based on the in-focus position detected by the contrast detection method. In the contrast detection method, a focus evaluation value indicating the contrast of an object is obtained from the video signal generated by using the image sensor of a digital camera, and the position of a focus lens where the focus evaluation value is maximized is set as an in-focus position. When detecting a position where a maximum focus evaluation value is obtained, changes in focus evaluation value are monitored while the focus lens is finely driven. The digital camera disclosed in Japanese Patent Laid-Open No. 2003-295047 corrects the in-focus position obtained by the phase difference detection method at the time of imaging by using the correction value obtained by focus calibration, and moves the focus lens to the in-focus position after the correction, thereby performing more accurate in-focus control.
In addition, according to Japanese Patent Laid-Open No. 2007-041095, the pseudo-object image generated inside a camera is displayed on an external display device, and an in-focus position is obtained with respect to the pseudo-object image by each detection method in the focus calibration mode. Disclosed is a camera which corrects the in-focus position obtained by the phase difference detection method from the detection result.
Recently, in a focus detection apparatus based on the phase difference detection method, as a focus detection area increases with respect to an imaging field angle in accordance with user's requirements, the number of detection points increase. This makes it necessary to consider a focus calibration method in accordance with a focus detection apparatus based on the phase difference detection method which is mounted in an image capturing apparatus.
However, the related art disclosed in Japanese Patent Laid-Open No. 2003-295047 described above makes no reference to focus calibration methods or display methods corresponding to different detection areas or detection point counts. In addition, the above related art only mentions that, with regard to an object used for in-focus position detection at the time of calibration, it is preferable to use, for accurate focus calibration, a dedicated chart rather than a general object.
According to the related art disclosed in Japanese Patent Laid-Open No. 2007-041095, in order to perform focus calibration, it is necessary to display a dedicated chart (pseudo-object image) on an external display device. For this reason, even if a user needs to perform focus calibration in a field, he/she cannot perform focus calibration without any external display apparatus.